Power supply control device

Abstract

The present disclosure provides a power supply control device. An output voltage is generated from an input voltage by switching driving an output stage based on a feedback voltage corresponding to the output voltage. An overcurrent protection signal is output when a value of a current flowing through the output stage exceeds a predetermined overcurrent threshold. An overcurrent protection operation is performed in response to the overcurrent protection signal, and the overcurrent protection operation limits an increase in the current flowing through the output stage exceeding the overcurrent threshold. The overcurrent threshold is set according to an elapsed time from a start of switching driving of the output stage.

1 . A power supply control device, configured to control an output stage of a switching power supply device that generates an output voltage from an input voltage, the power supply control device comprising:
 a switching control circuit, configured to switch and drive the output stage based on a feedback voltage corresponding to the output voltage, wherein the output voltage is generated from the input voltage through a switching drive of the output stage, wherein the switching control circuit includes:
 a threshold setting circuit, configured to set an overcurrent threshold; and 
 an overcurrent protection circuit, configured to
 output an overcurrent protection signal when a value of a current flowing through the output stage exceeds the overcurrent threshold, and 
 perform an overcurrent protection operation that limits an increase in the current flowing through the output stage exceeding the overcurrent threshold in response to an output of the overcurrent protection signal, wherein 
 
 the threshold setting circuit sets the overcurrent threshold according to an elapsed time from a start of the switching drive of the output stage. 
   
     
     
         2 . The power supply control device of  claim 1 , wherein the threshold setting circuit is configured to
 set the overcurrent threshold to a first threshold or a second threshold lower than the first threshold, and   switch the overcurrent threshold from the first threshold to the second threshold as the elapsed time increases.   
     
     
         3 . The power supply control device of  claim 2 , wherein
 the switching control circuit is configured to switch and drive the output stage so as to reduce an error between the feedback voltage and a comparison voltage,   the switching control circuit, after the start of the switching drive of the output stage,
 uses a soft-start voltage that gradually increases from an initial voltage lower than a predetermined reference voltage as the comparison voltage, and 
 uses the reference voltage as the comparison voltage after the soft-start voltage exceeds the reference voltage, and 
   the threshold setting circuit switches the overcurrent threshold from the first threshold to the second threshold according to the soft-start voltage that depends on the elapsed time.   
     
     
         4 . The power supply control device of  claim 3 , wherein the threshold setting circuit is configured to switch the overcurrent threshold from the first threshold to the second threshold when the soft-start voltage reaches a predetermined voltage higher than the reference voltage. 
     
     
         5 . The power supply control device of  claim 1 , wherein as the elapsed time increases and after the overcurrent threshold is continuously lowered from a first threshold to a second threshold lower than the first threshold, the threshold setting circuit is configured to set the overcurrent threshold as the second threshold. 
     
     
         6 . The power supply control device of  claim 5 , wherein
 the switching control circuit is configured to switch and drive the output stage so as to reduce an error between the feedback voltage and a comparison voltage,   the switching control circuit, after the start of the switching drive of the output stage,
 uses a soft-start voltage that gradually increases from an initial voltage lower than a predetermined reference voltage as the comparison voltage, and 
 uses the reference voltage as the comparison voltage after the soft-start voltage exceeds the reference voltage, and 
   after the overcurrent threshold is continuously lowered from the first threshold to the second threshold according to the soft-start voltage that depends on the elapsed time, the threshold setting circuit sets the overcurrent threshold as the second threshold.   
     
     
         7 . The power supply control device of  claim 6 , wherein
 the switching control circuit, after the start of the switching drive of the output stage, gradually increases the soft-start voltage to a predetermined upper limit voltage higher than the initial voltage, and   the threshold setting circuit is configured to
 continuously lower the overcurrent threshold from the first threshold to the second threshold according to the soft-start voltage during a rising period of the soft-start voltage, and 
 set the overcurrent threshold to the second threshold after the soft-start voltage reaches the upper limit voltage. 
   
     
     
         8 . The power supply control device of  claim 1 , wherein the switching drive of the output stage begins with supplying the input voltage to the power supply control device. 
     
     
         9 . The power supply control device of  claim 1 , comprising an enable terminal, configured to receive an enable signal, wherein the switching drive of the output stage begins when a level of the enable signal changes from a first level to a second level while the input voltage is supplying to the power supply control device. 
     
     
         10 . The power supply control device of  claim 1 , wherein
 the output stage includes:
 an output element comprising a switching element; and 
 a rectifier connected to the output element, 
   a coil is connected to a connection node between the output element and the rectifier, and   the output voltage is generated based on the current flowing through the coil by switching the output element between on and off during the switching drive of the output stage.   
     
     
         11 . A power supply control device, configured to control an output stage of a switching power supply device that generates an output voltage from an input voltage, the power supply control device comprising:
 an error voltage generation circuit, configured to generate an error voltage according to a difference between a feedback voltage corresponding to the output voltage and a predetermined reference voltage;   a control drive circuit, configured to perform a switching drive of the output stage based on the feedback voltage;   an overcurrent protection circuit, configured to output an overcurrent protection signal when the value of a current flowing through the output stage exceeds a predetermined overcurrent threshold; and   an error voltage change suppression circuit, wherein   the output voltage is generated from the input voltage through the switching drive of the output stage,   the control drive circuit, in response to the overcurrent protection signal, performs an overcurrent protection operation that limits an increase in the current flowing through the output stage exceeding the overcurrent threshold, and   the error voltage change suppression circuit is configured to suppress change in the error voltage based on the overcurrent protection signal.   
     
     
         12 . The power supply control device of  claim 11 , wherein
 the feedback voltage increases or decreases as the output voltage increases or decreases,   the error voltage generation circuit is configured to generate the error voltage in an error output wiring by outputting a current signal corresponding to the difference, to the error output wiring in a manner that
 the error voltage changes in a first direction when the feedback voltage is lower than the reference voltage, and 
 the error voltage changes in a second direction opposite to the first direction when the feedback voltage is higher than the reference voltage, and 
   the error voltage change suppression circuit is configured to suppress the change in the error voltage in the first direction based on the overcurrent protection signal.   
     
     
         13 . The power supply control device of  claim 12 , wherein
 in a state when the feedback voltage becomes lower than the reference voltage through execution of the overcurrent protection operation in response to the overcurrent protection signal,   the error voltage generation circuit is configured to output the current signal for changing the error voltage in the first direction to the error output wiring, and   the error voltage change suppression circuit is configured to suppress change in the error voltage in the first direction by changing the error voltage in the second direction based on the overcurrent protection signal.   
     
     
         14 . The power supply control device of  claim 12 , wherein
 a phase compensation circuit is disposed between the error output wiring and a potential point having a predetermined potential and configured to compensate for a phase of the error voltage,   the phase compensation circuit includes:
 a phase compensation resistor connected to the error output wiring; and 
 a phase compensation capacitor connected between the phase compensation resistor and the potential point, and 
   the error voltage change suppression circuit is configured to suppress change in the error voltage in the first direction by discharging accumulated charges of the phase compensation capacitor based on the overcurrent protection signal.   
     
     
         15 . The power supply control device of  claim 14 , wherein
 the error voltage change suppression circuit includes a discharge switch connected in parallel to the phase compensation capacitor, and   the accumulated charges in the phase compensation capacitor are discharged by turning on the discharge switch based on the overcurrent protection signal.   
     
     
         16 . The power supply control device of  claim 15 , wherein
 the overcurrent protection circuit is configured to output the overcurrent protection signal for a predetermined period of time when a value of the current flowing through the output stage exceeds the overcurrent threshold, and   the error voltage change suppression circuit is configured to turn on the discharge switch during an output period of the overcurrent protection signal.   
     
     
         17 . The power supply control device of  claim 15 , wherein
 during the switching drive of the output stage, a state of the output stage is switched between a first state in which the current flowing through the output stage is increased and a second state in which the current flowing in the output stage is decreased,   the overcurrent protection circuit is configured to
 start outputting the overcurrent protection signal when the value of the current flowing through the output stage exceeds the overcurrent threshold when the output stage is in the first state, and then, 
 stop outputting the overcurrent protection signal when the state of the output stage changes to the second state, and 
   the error voltage change suppression circuit is configured to turn on the discharge switch during the output period of the overcurrent protection signal.   
     
     
         18 . The power supply control device of  claim 12 , wherein
 the output stage includes:
 an output element comprising a switching element; and 
 a rectifier connected to the output element, 
   a coil is connected to a connection node between the output element and the rectifier,   the output voltage is generated based on the current flowing through the coil by switching the output element between on and off during the switching drive of the output stage,   the power supply control device further includes a slope voltage generation circuit configured to generate a slope voltage according to a current information of the coil,   the control drive circuit performs the switching drive of the output stage according to the error voltage and the slope voltage,   the slope voltage generation circuit monotonically changes the slope voltage in the first direction during an on period of the output element, and   the control drive circuit, after the output element is switched from off to on, switches the output element from on to off when the slope voltage reaches the error voltage in a process of changing the slope voltage in the first direction.   
     
     
         19 . The power supply control device of  claim 18 , wherein when the overcurrent protection signal is output when the value of the current flowing through the output stage exceeds the overcurrent threshold while the output element is controlled to be turned on, the control drive circuit is configured to
 switch off the output element in the overcurrent protection operation, and then   maintain the output element off at least until the value of the current flowing through the output stage falls below a predetermined release threshold, and the release threshold is lower than the overcurrent threshold.   
     
     
         20 . A power supply control device, configured to control an output stage of a switching power supply device that generates an output voltage from an input voltage, the power supply control device comprising:
 an error voltage generation circuit, configured to generate an error voltage according to a difference between a feedback voltage corresponding to the output voltage and a predetermined reference voltage;   a skip determination voltage generation circuit, configured to generate a skip determination voltage;   a skip signal generation circuit, configured to generate a skip signal having a first logical value or a second logical value based on the error voltage and the skip determination voltage; and   a control drive circuit, configured to
 perform a switching drive of the output stage according to the error voltage when the skip signal has the first logical value, while 
 stop the switching drive of the output stage when the skip signal has the second logical value, wherein 
   the output voltage is generated from the input voltage through the switching drive of the output stage, and   the skip determination voltage generation circuit changes the skip determination voltage according to a temperature of the power supply control device.   
     
     
         21 . The power supply control device of  claim 20 , wherein
 the feedback voltage increases or decreases as the output voltage increases or decreases,   the error voltage generation circuit is configured to
 change the error voltage in a first direction when the feedback voltage is lower than the reference voltage, while 
 change the error voltage in a second direction opposite to the first direction when the feedback voltage is higher than the reference voltage, 
   the skip signal generation circuit is configured to generate the skip signal based on a level relationship between the error voltage and the skip determination voltage, wherein   the skip signal generation circuit
 generates the skip signal having the first logical value when the skip determination voltage is different from the error voltage in the second direction, while 
 generates the skip signal having the second logical value when the skip determination voltage is different from the error voltage in the first direction, and 
   the skip signal generation circuit changes the skip determination voltage in the first direction as the temperature increases.   
     
     
         22 . The power supply control device of  claim 21 , wherein the skip signal generation circuit changes the skip determination voltage continuously or stepwise in the first direction as the temperature increases. 
     
     
         23 . The power supply control device of  claim 21 , wherein
 the first direction is an upward direction, and the second direction is a downward direction, and   the skip signal generation circuit is configured to
 generate the skip signal having the first logical value when the skip determination voltage is lower than the error voltage, while 
 generate the skip signal having the second logical value when the skip determination voltage is higher than the error voltage. 
   
     
     
         24 . The power supply control device of  claim 21 , wherein
 the first direction is a downward direction, and the second direction is an upward direction, and   the skip signal generation circuit is configured to
 generate the skip signal having the first logical value when the skip determination voltage is higher than the error voltage, while 
 generate the skip signal having the second logical value when the skip determination voltage is lower than the error voltage. 
   
     
     
         25 . The power supply control device of  claim 20 , wherein
 the output stage includes:
 an output element comprising a switching element; and 
 a rectifier connected to the output element, 
   a coil is connected to a connection node between the output element and the rectifier,   the output voltage is generated based on the current flowing through the coil by switching the output element between on and off during the switching drive of the output stage,   the power supply control device further includes a slope voltage generation circuit configured to generate a slope voltage according to a current information of the coil, and   the control drive circuit performs the switching drive of the output stage according to the error voltage and the slope voltage when the skip signal has the first logical value.